1. Field of the Invention
The present invention relates to an actuator used for, for example, optical apparatuses, etc. which have a holder with a movement hole and a lens barrel for accommodating the lens barrel, and which have a zooming function that the lens barrel moves within the movement hole, etc.
2. Description of the Related Art
A driving mechanism for a lens barrel is disclosed inn FIG. 3 of Japanese Unexamined Patent Application Publication No. 5-249362 (hereinafter, referred to as Patent Document 1). Patent Document 1 discloses provision of an optical apparatus which can perform a focus-switching operation and a focusing operation with a single motor by a combination of the motor, a pinion, gear, etc.
However, the driving mechanism for a lens barrel with the combination of the motor, the gear, etc. is difficult to be assembled into small electronic apparatuses, particularly, mobile telephones.
Further, in order to make the lens barrel perform various kinds of complex operations, an intricate driving mechanism is required. As a result, not only an increase in size of the driving mechanism may be caused, but also an increase in manufacturing cost and a reduction in yield rate may be caused.
Accordingly, it is also considered that conventionally known electrostatic actuators, piezoelectric actuators, etc. are used as the driving mechanism. However, these actuators have problems in that expansion or contraction ratio is low, a high driving force cannot be obtained, the degree of freedom in structure is low, etc.
Meanwhile, actuators called conductive high-polymer actuators (hereinafter referred to as artificial muscle) have been paid attention to as new actuators substituted for the conventional actuators.
As a known document on the artificial muscle, there is Japanese Unexamined Patent Application Publication No. 2001-286162 (hereinafter referred to as Patent Document 2).
Patent Document 2 discloses using the artificial muscle as valve devices, pump devices, bimorphs, etc.
However, Patent Document 2 does not disclose using the artificial muscle as the driving mechanism for a lens barrel at all.
Particularly, when the artificial muscle is used as the driving mechanism for a lens barrel, it was found that various kinds of study on suitably driving the lens barrel are necessary.